1. Field of Invention
The present invention generally relates to a wireless identifier reader system, and more particularly to a probability time division multiplexing polling method and a wireless identifier reader controller thereof, wherein the probability time division multiplexing polling method and the wireless identifier reader controller are used in the wireless identifier reader system.
2. Description of Prior Art
The wireless communication technology is becoming more and more mature, and is applied on the daily life, for example, the wireless identifier reader system is applied on the ticket system of mass rapid transit (MRT) system. When the passenger comes into or departs from the MRT station, he or she must put the ticket card in the sensing region of the wireless identifier reader, so as to come into or depart from the MRT station successfully. The wireless identifier reader adopted by the MRT system has a smaller sensing region, and therefore the wireless identifier readers could not interfere with each other.
Under some conditions, the larger sensing regions of the wireless identifier readers in the wireless identifier reader system are demanded. For example, each of visitors is assigned an identifier tag in the exhibitive place, and each of exhibitive regions has at least a wireless identifier reader having the larger sensing region. When the visitor walks to the exhibitive region, the wireless identifier reader directly detects the identifier tag carried by the visitor, so as to store the visit record of the visitor. The wireless identifier reader having the larger sensing region is not same as the wireless identifier reader adopted by the MRT system, and the visitor need not take out the identifier tag to put it in the sensing region of the wireless identifier reader. However the wireless identifier readers could interfere with each other potentially due to the larger sensing regions of the wireless identifier readers.
Referring to FIG. 1A and FIG. 1B, FIG. 1A is a plan view of the exhibitive place, and FIG. 1B is block diagram of a wireless identifier reader system. The exhibitive place of FIG. 1A is divided into several exhibitive regions A1-A10, and each exhibitive region Ai (i is an integer from 1 to 10) has at least a wireless identifier reader WRi, wherein the wireless identifier reader WRi may be a radio frequency identifier reader (RFID reader). The wireless identifier reader WRi is used to detect the identifier tag carried by the visitor, such as a RFID tag. In FIG. 1B, wireless identifier readers WR1-WR5 of the several neighboring exhibitive regions A1-A5 are connected to a hub HUB1, and the hub HUB1 is connected to a wireless identifier reader controller CR1. The wireless identifier reader controller CR1 is used to control the wireless identifier readers WR1-WR5 to be turned on or off. When one of the wireless identifier readers WR1-WR5 in the terminal end detects the identifier tag carried by the visitor, the wireless identifier reader controller CR1 transmit the identifier information of the detection result to the message queue MQ via the Ethernet, and then the listener LN in the back end continuously writes the content in the message queue into the database DB.
In the similar manner, wireless identifier readers WR6-WR10 of the several neighboring exhibitive regions A6-A10 are connected to a hub HUB2, and the hub HUB2 is connected to a wireless identifier reader controller CR2. The wireless identifier reader controller CR2 is used to control the wireless identifier readers WR6-WR10 to be turned on or off. When one of the wireless identifier readers WR6-WR10 in the terminal end detects the identifier tag carried by the visitor, the wireless identifier reader controller CR2 transmit the identifier information of the detection result to the message queue MQ via the Ethernet, and then the listener LN in the back end continuously writes the content in the message queue into the database DB. Besides, the database DB is connected to a client querying device CS, such as a personal computer or the computers of other kinds. The client querying device CS is used to query the database, so as to search the visit record of the visitor which is stored in the database DB, and the value of the products or the service exhibited in the exhibitive region can be analyzed according to the stored visit record.
To solve the problem of the potential interference between the wireless identifier readers, some documents and patents disclose some solutions for the problem of the potential interference. The ROC patent M315380 discloses a fixed time polling method to turn on or off the wireless identifier readers. The fixed time polling method only allows one of the wireless identifier readers being turned on at the same time. The WIPO publication WO/2006/080976 discloses a managing system solving the problem of the potential interference. When the wireless identifier readers detects an identifier tag, the managing system selects a appropriate one wireless identifier reader to transmit the identifier information of the identifier tag, and disables the neighboring wireless identifier readers of the appropriate one to transmit the identifier information of the identifier tag simultaneously. Besides, the WIPO publication WO/2007/005135 discloses a time-frequency division multiplexing polling method to turns on or off a plurality of wireless identifier readers. However, the WIPO publication WO/2007/005135 does not disclose and teach how to perform time division multiplexing.